Power transmission system IC card and information communication system using IC card

ABSTRACT

The present invention comprises a power transmission system, an IC card, and an information communication system using an IC card. In the power transmission system, power is transmitted by radio from the power transmission device to the IC card. In the IC card, the transmitted induced power is converted into a DC voltage, the transmitted induced power or a voltage corresponding to the induced power is detected, and a desired DC voltage to be suppled to the internal circuit is obtained in controlling resistance the detected induced power or the voltage corresponding to the induced power.

BACKGROUND OF THE INVENTION

The present invention relates to a power transmission system, an IC cardand an information communication system using an IC card, whereincommutation tickets, railway tickets, bus tickets, etc. to be used atwickets in railway stations or on buses will be replaced with IC cards,and when an IC card is made to pass a reader/writer, being provided at awicket in a railway station or on a bus, with noncontact or in closeproximity to it, power can be transmitted from the reader/writer to theIC card by radio.

It has been known that power can be supplied to an IC card from a powersupply side by a noncontact method using rays of light or magneticfields.

When commutation tickets, railway tickets, bus tickets, etc. to be usedat wickets in railway stations or on buses will be replaced with ICcards, and when a user passes an IC card through a reader/writerprovided at a wicket in a railway station or on a bus with noncontact,the distance between the IC card and the reader/writer may vary much.When the reader/writer is so adjusted that proper power can betransmitted from the reader/writer to the IC card when the distancebetween the IC card and the reader/writer is comparatively large, thenin a case where the distance between the reader/writer and the IC cardis small, excessive power may be transmitted from the reader/ writer tothe IC card, which may cause a malfunction or breakage of the IC card.

In other words, in the prior art, careful consideration was not given toa point that proper power shall be stably transmitted to an IC card froma reader/ writer even though the distance between the IC card and thereader/writer may be largely varied.

Prior art in which it is intended to stably supply power from areader/writer to an IC card even if the distance between the IC card andthe reader/writer is largely varied is explained in Japanese PatentsLaid-open No. Hei 7-85233 and Laid-open No. 9-62816.

In the Japanese Patent Laid-open No. 7-85233, following are described:among noncontact type data carriers of electromagnetic coupling system,in the case of movable equipment having a function to be able to receivedata including a control signal from fixed equipment, a rectifiercircuit composed of a rectifier D1 and a capacitor C2, and a variableresistor element composed of a transistor T2, resistor R3 and resistorR4 being controlled by a DC voltage obtained from the rectifier circuitare connected to a receiving coil of the data carrier in parallel, andan excess power will be consumed in the variable resistor elements.Further it is described in the Japanese Patent Laid-open No. Hei 7-85233that a signal detector circuit composed of a rectifier D2, a resistor R1and a capacitor C3 which detects an amplitude-modulated wavesuperimposed on a AC voltage induced in the receiving coil and transmitsthe detected data to a main circuit of the data carrier as an inputsignal, and an amplitude modulator circuit which receives the outputsignal of the main circuit of the data carrier for switching atransistor T1, and being composed of the transistor T1 which transmitsdata from the data carrier to the fixed equipment, a capacitor C4 and aresistor R2 are connected to the receiving coil of the data carrier inparallel. In the prior art as mentioned in the above, a resonant circuitis not formed in the receiving coil of the data carrier, so that in acase where the distance between the transmitting coil on the fixed sideand the receiving coil on the data carrier side is large, an enoughvoltage is not induced in the receiving coil and it is made difficult toobtain the power required by the main circuit of the data carrier. Thereis also another problem in the prior art. Since a half-wave rectifier isadopted in the prior art, a large ripple is produced, which requires alarge smoothing capacity; therefore, it is made difficult to incorporatea capacitor of a large capacity in a data carrier in miniaturizing it.

It is described in the Japanese Patent Laid-open No. Hei 9-62816 that areceiving signal level of a resonance circuit of an antenna fortransmitting and receiving data is detected and the quality factor Q ofthe antenna resonance circuit is varied by changing the variableresistor element according to the detected voltage in order to adjust areceiving signal level to a desirable value.

In these prior art, since a variable resistor element is directlyconnected to a receiving antenna in parallel, there is a problem in thatthe temperature rise in the variable resistor element is large and thesize of a pressure protection circuit becomes large.

SUMMARY OF THE INVENTION

The purpose of the present invention is to solve the above-mentionedproblems and offer an IC card and a power transmission system by radioin which it is made possible to stably supply power by radio from areader/ writer to the internal circuit of an IC card in miniaturizingthe elements of a pressure protection circuit and decreasing thetemperature rise in a variable impedance circuit provided in an IC cardeven though the distance between the IC card and the reader/writer maybe largely varied.

Another object of the present invention is to offer an IC card and apower transmission system by radio in which the power can be stablysupplied to the internal circuit of the IC card by radio from a readerand/or writer by only making the IC card pass the reader and/or writerwith noncontact or in close proximity to it by improving theresponsibility of the system in miniaturizing the elements in a pressureprotection circuit and decreasing the temperature rise in a variableimpedance circuit.

A further object of the present invention is to offer an IC card and aninformation communication system using an IC card in which it is madepossible to supply power stably from a reader and/or writer to the ICcard with noncontact in miniaturizing the elements in the pressureprotection circuit and decreasing the temperature rise in the variableimpedance circuit provided in the IC card and to perform informationcommunication with high reliability between the reader and/or writer andthe IC card.

Yet another object of the present invention is to offer a powertransmission system by radio, an IC card and an informationcommunication system using the IC card. In the power transmission systemby radio it is so arranged that power can be stably supplied even whenthe distance between an IC card and a reader/writer is largely varied indecreasing the temperature rise in the variable impedance circuit bycontrolling the static capacity for the induced power received on the ICcard side.

A still further object of the present invention is to offer a powertransmission system by radio, an IC card and an informationcommunication system using the IC card. In the power transmission systemby radio it is so arranged that proper power can be stably supplied tothe IC card by radio from the power transmission portion of thereader/writer by only passing the IC card through the reader/writer withnoncontact or in proximity to it and information can be communicatedbetween the reader/writer and the IC card with high reliability.

In order to achieve the above-mentioned objects, the present inventionis a power transmission system in which power is transmitted by radiofrom a power transmitting device (reader and/or writer device) to an ICcard. The IC card comprises: an antenna having a resonance circuit forreceiving the transmitted radio wave, a full wave rectifier circuit forrectifying an induced power received by the antenna, a power supplycircuit which converts a DC voltage output from the full wave rectifiercircuit into a power supply voltage, a detector circuit which detectsthe DC voltage output from the full wave rectifier circuit, an impedancecontrol circuit portion which produces a desired power supply voltagefrom the DC voltage detected in the detector circuit by controlling theimpedance of the circuit, and an internal circuit to be supplied withthe desired power supply voltage obtained from the impedance controlcircuit.

The present invention is also a power transmission system in which poweris transmitted by radio from a power transmission device to an IC card,wherein the IC card comprises: a receiving portion which receives thetransmitted radio wave and produces induced power, a rectifier circuitportion which converts the induced power in the receiving portion into aDC voltage, a variable impedance circuit portion in which the DC voltageobtained in the rectifier circuit is controlled by varying the impedanceof the circuit based on the induced power detected in the detectorcircuit portion or a voltage corresponding to the induced power, and aninternal circuit to be supplied with a controlled DC voltage from thevariable-impedance control circuit.

The present invention is also a power transmission system in which poweris transmitted by radio from the power transmission device to an ICcard. In the IC card, the transmitted induced power is converted into aDC voltage, the transmitted induced power or a voltage corresponding tothe induced power is detected, and a power supply voltage of a desiredDC voltage to be supplied to the internal circuit is obtained bycontrolling a static capacity based on the detected induced power or avoltage corresponding to the induced power.

The present invention is a power transmission system in which power istransmitted by radio from a power transmission device to an IC card. TheIC card comprises: a rectifier circuit which converts the transmittedinduced power into a DC voltage, an internal circuit to be supplied withthe DC voltage obtained from the rectifier circuit, a detector circuitwhich detects the transmitted induced power or a voltage correspondingto the induced power, and a static capacity control circuit whichobtains a power supply voltage of a desired DC voltage to be supplied tothe internal circuit by controlling the static capacity based on theinduced voltage or a voltage corresponding to the induced power which isdetected in the detector circuit.

The present invention is a power transmission system in which power istransmitted by radio from a power transmitting device to an IC card. TheIC card comprises the functions as shown below: the transmitted inducedpower is converted into a DC voltage to be supplied to an internalcircuit, the transmitted induced power or a voltage corresponding to theinduced power is detected, and the information about the detectedinduced power or a voltage corresponding to the induced power istransmitted by radio to the power transmitting device. The powertransmitted from the power transmitting device is controlled based onthe above-mentioned transmitted information.

The present invention is a power transmission system in which power istransmitted by radio from a power transmitting device to an IC card. TheIC card comprises the function to convert the transmitted induced powerinto a DC voltage and to supply the DC voltage to the internal circuit,and also to detect the information concerning the relative position ofthe IC card to that of the power transmitting device. The powertransmitted from the power transmission device is controlled based onthe above-mentioned detected information.

The present invention is a power transmission system in which power istransmitted by radio from a power transmitting device to an IC card. TheIC card comprises the function to convert the transmitted induced powerinto a DC voltage and to supply the DC voltage to the internal circuitand to detect the information concerning the relative position of the ICcard to that of the power transmitting device. A desired DC voltage canbe obtained in controlling the impedance of a circuit in the IC cardbased on the detected information.

The present invention is an IC card which comprises: an antenna having aresonance circuit for receiving a transmitted radio wave, a full waverectifier circuit for rectifying an induced power received with theantenna, a power supply circuit for converting the DC voltage obtainedfrom the full wave rectifier circuit into a power supply voltage, adetector circuit for detecting the DC voltage rectified in the full waverectifier circuit, an impedance control circuit which controls theimpedance of the circuit for making the detected DC voltage a desired DCvoltage and making the power supply voltage converted in the powersupply circuit a desired power supply voltage, and an internal circuitto be supplied with the desired power supply voltage obtained from theimpedance control circuit portion.

The present invention is an IC card which comprises: a receiver portionwhich receives a radio wave to produce an induced power, a rectifiercircuit portion for rectifying the induced power generated in thereceiver portion to convert the induced power to a DC voltage, adetector circuit portion which detects an induced power obtained in thereceiver portion or a voltage corresponding to the induced power, avariable impedance control circuit portion which controls the DC voltageobtained from the rectifier circuit portion based on the induced powerdetected in the detector circuit portion or a voltage corresponding tothe induced power, and an internal circuit to be supplied with acontrolled DC voltage from the variable impedance control circuitportion.

The present invention comprises an IC card in which an impedance in thevariable impedance circuit portion is formed with a resistor.

The present invention is an IC card in which the full wave rectifiercircuit, the power supply circuit, the detector circuit, the impedancecontrol circuit, and the internal circuit are composed with one chip.

The present invention is an IC card which comprises: a receiver portionwhich receives an induced power by radio, a rectifier circuit portionwhich rectifies the induced power received in the receiver portion toconvert it into a DC voltage, a detector circuit portion which detectsthe induced power obtained from the receiver portion or a voltagecorresponding to the induced power, a static capacity control circuitportion which obtains a desired DC voltage from the rectifier circuitportion by controlling the static capacity based on the induced powerdetected in the detector circuit portion or a voltage corresponding tothe induced power, and an internal circuit which is supplied with a DCvoltage from the rectifier circuit portion being controlled by thestatic capacity control circuit portion.

The present invention is an information communication system using an ICcard which comprises a reader and/or writer device (unit) having aninformation communication portion and a power transmitting portion andpower is transmitted by radio from the power transmitting portion to anIC card.

The IC card comprises: a rectifier circuit portion which rectifies theinduced power transmitted from the reader and/or writer to convert theinduced power into a DC voltage, a detector circuit portion whichdetects the induced power obtained from the receiver portion or avoltage corresponding to the induced power, a variable impedance controlcircuit portion which controls the impedance of the circuit according tothe DC voltage obtained from the rectifier circuit portion based on theinduced power detected in the detector circuit portion or a voltagecorresponding to the induced power, and an internal circuit whichobtains a desired DC voltage from the variable impedance controlcircuit. The information communication system is so designed that aninformation communication can be performed using a radio wave betweenthe internal circuit of the IC card and the information communicationportion of the reader and/or writer device.

Transmitted to the IC card or a voltage corresponding to the inducedpower is detected, and a desired DC voltage is obtained in controllingthe impedance base on the detected induced power or a voltagecorresponding to the induced power and the desired DC voltage issupplied to the internal circuit. The present invention is soconstituted that it is possible to perform information communication byradio between the internal circuit of the IC card and the informationcommunication portion of the reader and/or writer device.

The present invention is an information communication system using an ICcard, which comprises reader and/or writer device having an informationcommunication portion and a power transmission portion and power istransmitted by radio from the power transmitter portion to the IC cardby radio. The IC card comprises: an antenna having a resonance circuitfor receiving a radio wave transmitted from the reader and/or writerdevice, a full wave rectifier circuit for rectifying the induced powerreceived in the antenna, a power supply circuit which converts the DCvoltage rectified in the full wave rectifier circuit into a power supplyvoltage, a detector circuit which detects the DC voltage rectified inthe full wave rectifier circuit, an impedance control circuit whichcontrols the impedance of the circuit to make a detected DC voltagedetected in the detector circuit a desired DC voltage and to make thepower supply voltage converted in the power supply circuit a desiredpower supply voltage, and an internal circuit to be supplied with thedesired power supply voltage obtained from the impedance controlcircuit.

The information communication system is so designed that the informationcommunication can be performed by a radio wave between the internalcircuit of the IC card and the information communication portion of thereader and/or writer device.

The present invention is an information communication system using an ICcard which comprises a reader and/or writer device having an informationcommunication portion and a power transmission portion which transmitspower from the power transmission portion to the IC card by radio. Inthe IC card, following operations are performed: the induced powertransmitted from the reader and/or writer device is converted into a DCvoltage and it is supplied to the internal circuit, the induced powertransmitted to the IC card or a voltage corresponding to the inducedpower is detected, and the information concerning the detected inducedpower or the voltage corresponding to the induced power is transmittedto the power transmission portion of the reader and/or writer device byradio. The reader and/or writer controls the power to be transmittedfrom the power transmission portion based on the information sent fromthe IC card. The information communication system is so designed thatinformation communication can be performed between the internal circuitof the IC card and the information communication portion of the readerand/or writer device.

The present invention is an information communication system using an ICcard, wherein the transmission of power by radio from the reader and/orwriter to the IC card and the communication of information by radiobetween the internal circuit of the IC card and the informationcommunication portion of the reader and/or writer device are performedwith a common antenna.

The present invention is an information communication system, using anIC card, wherein the reader and/or writer device comprises: a powersupply portion which generates a signal to be used for the transmissionof power, an encoder circuit for encoding input data for transmission, amodulator which executes amplitude modulation of a signal obtained fromthe encoder circuit and superimposes it on the signal obtained from thepower supply portion, a feeder circuit for feeding power based on thesignal obtained from the modulator, and an antenna for generating aradio wave corresponding to the fed current by the feeder circuit.

The present invention is an information communication system using an ICcard, wherein the internal circuit of the IC card comprises: a decodercircuit which performs waveform shaping and decodes a modulated wave forcommunication detected by the antenna, a microcomputer which inputsreceived data decoded in the decoder circuit and outputs transmissiondata, an encoder circuit which encodes the transmitting data output fromthe microcomputer, and a modulator which modulates a signal and inputsit to the antenna based on the signal encoded in the encoder circuit.

As explained in the above, according to the above-mentionedconstitution, it is made possible to realize a power transmission systemby radio and an IC card, wherein even though the distance between the ICcard and the reader and/or writer device (power transmitting device) islargely varied, power can be stably transmitted by radio from the readerand/or writer device to the internal circuit of the IC card inminiaturizing a pressure protection circuit provided in the IC card anddecreasing the temperature rise in a variable impedance circuit. Inparticular, the realization of miniaturization of the elements of thepressure protection circuit and the low temperature rise in the variableimpedance circuit made it possible to constitute an IC card with anantenna for receiving a radio wave and elements of one-chipconstitution, which caused to realize a low cost IC card.

According to the above-mentioned constitution, a power transmissionsystem by radio and an IC card can be realized, wherein power can betransmitted from the reader and/or writer device to the IC card by radiousing a coil-shaped antenna or a spiral antenna on the IC card, andpower can be supplied stably by radio from the reader and/or writerdevice to the internal circuit of the IC card by only making an IC cardpass the reader and/or writer device with noncontact or in the proximityto it in miniaturizing the elements in the pressure protection circuit,decreasing the temperature rise in the variable impedance circuit, andimproving the responsibility of the circuit.

According to the above-mentioned constitution, a power transmissionsystem by radio, an IC card, and an information communication systemusing an IC card can be realized, wherein power can be stably suppliedto the IC card even though the distance between the IC card and thereader and/or writer is largely varied in decreasing the temperaturerise in the variable impedance circuit by controlling the induced powerreceived on the side of the IC card by varying the static capacity inthe variable impedance circuit.

According to the above-mentioned constitution, a power transmissionsystem by radio, an IC card, and an information communication systemusing the IC card can be realized, wherein proper power can betransmitted from the power transmission portion of the reader and/orwriter device to the IC card by radio by only making the IC card passthe reader and/or writer with noncontact or in proximity to it. Thus,power is stably supplied to the internal circuit of the IC card, and thecommunication of information of high reliability can be performedbetween the reader and/or writer device and the IC card.

According to the above-mentioned constitution, an informationcommunication system using an IC card can be realized, wherein power isstably supplied from the reader and/or writer to the IC card withnoncontact, and the communication (transmission and reception) ofinformation of high reliability can be performed between the readerand/or writer device and the IC card.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a schematic of a power transmission system according to thepresent invention, in which power is transmitted by radio from a readerand/or writer device provided at a wicket in a railway station or on abus to an IC card which is passed the reader and/or writer device withnoncontact or in proximity to it;

FIG. 2 shows a power transmission system by radio according to thepresent invention;

FIG. 3 shows the relation between d and VL, where d denotes the distancebetween a coil of a power supply circuit provided in a reader and/orwriter and an IC card, and VL denotes an induced voltage VL obtainedfrom an rectifier circuit;

FIG. 4 shows a schematic of a first embodiment of the power transmissionsystem by radio according to the present invention;

FIG. 5 shows a schematic of a second embodiment of a power transmissionsystem by radio according to the present invention;

FIG. 6 shows a concrete form of the variable impedance circuit 30 shownin FIG. 4 in the first embodiment;

FIG. 7 shows a state where an induced voltage is controlled within anallowable range owing to impedance control;

FIGS. 8(a) and 8(b) show a concrete form of the variable impedancecircuit 30 shown in FIG. 4 in the second embodiment;

FIGS. 9(a) and 9(b) show a concrete form of the variable impedancecircuit 30 shown in FIG. 4 in a third embodiment;

FIG. 10 shows a schematic view of a power transmission control system byradio in the third embodiment according to the present invention;

FIG. 11 shows a schematic view of a power transmission control system byradio in a fourth embodiment according to the present invention;

FIG. 12 shows a schematic view of the whole of the present inventionincluding the part in which an IC card functions the roles of railwaytickets, commutation tickets, etc. in transmitting or receiving theinformation concerning railway tickets, commutation tickets, etc. byradio in the first embodiment;

FIG. 13 shows a plan view showing the mounted state of elements on an ICcard according to the present invention;

FIG. 14 shows a schematic view of the whole of the present inventionincluding the part in which an IC card functions the roles of railwaytickets, commutation tickets, etc. in transmitting or receiving theinformation concerning railway tickets, commutation tickets, etc. byradio in the second embodiment; and

FIG. 15 shows the relation between the power transmitting wave and themodulated wave for the data communication according to the presentinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the following, the forms of embodiments of a power transmissionsystem by radio and an IC card according to the present invention willbe explained referring to the drawings.

FIG. 1 is a schematic view of a power transmission system according tothe present invention in which power is transmitted by radio from areader and/or writer 1 provided at a wicket in a railway station or on abus to an IC card 2 which is to be passed the reader and/or writer 1with noncontact or in proximity to it. The IC card 2 is passed thereader and/or writer 1 provided at the wicket in a railway station or ona bus by an user with noncontact, at a distance of about 5 to 20 cm. Inthat case, the information concerning railway tickets, commutationtickets, etc. is communicated by radio between the reader and/or writerand the IC card; thereby, the IC card will be able to perform the roleof a railway ticket, commutation ticket, or the like.

FIG. 2 shows a schematic view of a power transmission system by radioaccording to the present invention. A reference numeral 21 denotes apower supply circuit in the reader and/or writer 1 provided at a wicketin a railway station or on a bus. The power supply circuit 21 comprises:a power supply 22 which generates a high frequency voltage of 13.56 MHz,an impedance matching circuit 23 which prevents reflection at a junctionpoint, and a coil 24 which transmits power of about 2 to 5 W of 13.56MHz by radio. The IC card comprises an induced voltage generator portion28 which is composed of a coil 26 which receives power by radio from thepower supply circuit 21 provided in the reader and/or writer and arectifier circuit 27 which converts the high frequency power received bythe coil 26 into a DC voltage of the order of 7 to 15 V, and an internalcircuit 29 (constituted with an IC chip, for example) which is operatedwith a DC voltage of the order of 7 to 10 V generated in the inducedvoltage generator portion 28.

In order to be able to supply a desired DC voltage to the internalcircuit 29, even though the distance between the IC card 2 and thereader and/or writer 1 may be extremely large, a resonance circuit witha tuning capacitor 25 is provided in the coil 26 to be able to obtain alarge induced voltage. The coil 26 has a multilayer structure of morethan 2 layers in which a spiral-shaped antenna coil is woundcontinuously in the same direction, so that stray capacitance betweenwindings and the inductance of the coil may constitute a resonancecircuit. As a result, a tuning capacitor 25 may not be needed or anextremely small one will do the work.

In order to transmit power by radio, a coil (a coil-shaped orspiral-shaped antenna) 24 and a coil (a coil-shaped or spiral-shapedantenna) 26 are used for the purpose of improving the responsibility ofthe system to be able to supplying power to the internal circuitconstituted with an IC chip, for example) of the IC card 2 in less than0.1 sec. It has a merit to improve the strength of the IC card 2 againstdeformation by forming the coil 26 on the IC card 2. Therefore, if it ispossible to transmit power to the internal circuit 29 of the IC card 2in less than 0.1 sec., a light emitting element and a light receivingelement can be used in place of the coils 24 and 26.

FIG. 3 shows the relation between d and VL, where d denotes the distancebetween the coil 24 of the power supply circuit 21 provided in a readerand/or writer 1 and the IC card 25, and VL denotes the induced voltageobtained from the rectifier circuit 27. As shown in FIG. 3, in the casewhere the system is so designed that when the distance d between thecoil 24 of the power supply circuit 21 and the IC card 25 is at itsmaximum value d2 of about 20 cm, the allowable minimum voltage Vmin ofabout 2 to 4 V can be obtained, when the distance d between the coil 24of the power supply circuit 21 is at its minimum value d1 of about 5 cm,the induced voltage VL becomes the order of 40 V which largely exceedsthe allowable maximum voltage Vmax which may cause malfunction in theinternal circuit 29 or breakage of it.

Accordingly in the present invention, the induced voltage VL obtainedfrom the rectifier circuit 27 shall be constantly controlled to be inthe allowable range of the induced voltage, from Vmin to Vmax, even whenan IC card is passed the reader and/or writer 1 with noncontact at adistance of about 5 to 20 cm.

In the next step, the form of a first embodiment of a power transmissionsystem by radio according to the present invention will be explainedreferring to FIG. 4. FIG. 4 shows a schematic view showing the form ofthe first embodiment of the power transmission control system by radioaccording to the present invention. The power supply circuit 21 providedin the reader and/or writer 1 has the same constitution as that shown inFIG. 2. An induced voltage generator portion 28 a is composed of thecoil 26 and the rectifier 27 shown in FIG. 2 added with the followingcircuits: a variable impedance circuit 30 which supplies a controlledhigh frequency power to the rectifier circuit 27 in controlling the highfrequency power obtained from the coil 26 by varying its impedance, avoltage detector circuit 31 which detects the induced voltage VLobtained from the rectifier circuit 27, and a control circuit 32 whichcontrols the variable impedance circuit 30 by varying its impedancebased on the induced voltage detected in the induced voltage detectorcircuit 31. The internal circuit 29 in the IC card 2 is the same as thatshown in FIG. 2. The voltage detector circuit 31, as shown by a chainline, can be a circuit which calculates the mean value of inducedvoltages by detecting a high frequency power (a high frequency voltage)obtained from the variable impedance circuit 30, for example.

In an arrangement as shown in the above, the voltage detector circuitdetects the induced voltage VL obtained from the reifier circuit 27 andwhen it detects a voltage which deviates out of the allowable inducedvoltage range Vmin to Vmax, the impedance of the variable impedancecircuit 30 is controlled by the control circuit 32, and the highfrequency power obtained from the coil 26 is supplied to the rectifiercircuit 27 being controlled to be a proper value; thereby, a voltagewhich is constantly kept in the allowable induced voltage range can beobtained from the rectifier circuit 27. In the result, even when thedistance between the reader and/or writer 1 and the IC card 2 approaches5 cm, it is possible to supply a voltage in the allowable range of theinduced voltage to the internal circuit 29. In the above, it is possibleto constitute the rectifier circuit 27 and the internal circuit 29 withone IC chip.

In the next step, a second embodiment of the power transmission controlsystem by radio according to the present invention will be explainedreferring to FIG. 5. FIG. 5 shows a schematic view of the secondembodiment of the power transmission control system according to thepresent invention. In the second embodiment shown in FIG. 5, a differentpoint from the first embodiment shown in FIG. 4 is in that the variableimpedance circuit 30 is provided following the rectifier circuit 27. Theconstitution of the power supply circuit 21 provided in the readerand/or writer is the same as that shown in FIG. 2. The induced voltagegenerator portion 28 a in the IC card 2 is composed of a rectifiercircuit 27 which converts the high frequency power obtained from thecoil 26 into a DC voltage VL, a voltage detector circuit 31 whichdetects the DC voltage VL obtained from the rectifier circuit 27, avariable impedance circuit 30 which supplies a controlled DC voltage tothe internal circuit 29, the controlled DC voltage which is obtainedfrom the DC voltage output from the rectifier circuit 27 beingcontrolled by varying its impedance based on the induced voltagedetected by the voltage detector circuit 31, and the control circuit 32which controls the impedance of the variable impedance circuit 30 tovary. The internal circuit 29 in the IC card 2 is the same as that shownin FIG. 2.

In the arrangement as mentioned in the above, the voltage detectorcircuit 31 detects the rectified induced voltage VL obtained from therectifier circuit 27 and when it is detected that the voltage deviatesout of the allowable induced voltage range, Vmin to Vmax, the impedanceof the variable impedance circuit is controlled by the control circuit32 to correct the deviation, thus a DC voltage obtained from therectifier circuit 27 is controlled and supplied to the internal circuit29; thereby, a voltage in the range of allowable induced voltage can beconstantly obtained from the rectifier 27. In the result, even when thedistance between the reader and/or writer 1 and the IC card 2 approaches5 cm it is possible to supply a voltage in the allowable range to theinternal circuit 29.

FIG. 6 shows a concrete form of the variable impedance circuit 30 shownin FIG. 4 in the first embodiment. In the variable impedance circuit,there are two circuit elements, an resistor R1 and an electron switch 1connected in series and an resistor R2 and an electron switch 2connected in series, and a coil 26 is connected with bothabove-mentioned circuit elements in parallel, which constitutes thevariable impedance circuit 30. The ON-OFF operations of these electronswitches, S1 and S2, are controlled by control signals from the controlcircuit 32. As shown in FIG. 7, when the distance between the coil 24 ofthe power supply circuit 21 and the coil 26 of the IC card 2 beingdenoted by d decreases to a smaller one being off from d2, a large valueof d, and the rectified induced voltage VL exceeds Vmax, at first, theelectron switch S1 is made ON in the state where the electron switch S2is kept OFF by a control signal from the control circuit 32, then theresistor R1 is connected and the induced voltage VL is lowered to theVmim. When the coil 26 of the IC card 2 further approaches the coil 24of the power supply circuit and the induced voltage VL exceeds the Vmaxagain, the electron switch S2 is made ON in the state where the electronswitch S1 is kept ON, then both resistors R1 and R2 are connected andthe rectified induced voltage VL is lowered to the Vmin; therefore, evenwhen the distance between the coil 26 of the IC card and the coil 24 ofthe power supply circuit is decreased to d1, it will be possible to keepthe voltage VL not to exceed the Vmax. The allowable range between theVmin and Vmax can be made narrower by increasing the number ofresistors. As mentioned in the above, when the variable impedancecircuit 30 is constituted with a circuit in which a resistor R1 and anelectron switch S1 are connected in series and also a resistor R2 and anelectron switch S2 are connected in series, and both circuit elementsare connected to the coil 26 in parallel, the variable impedance circuit30 can be an excellent circuit in responsibility. The variable impedancecircuit 30 mentioned in the above can be applied to the variableimpedance circuit 30 composed of a variable resistor element shown inFIG. 5. In particular as shown in FIG. 14, a variable impedance circuit30 is provided next to a constant voltage power supply circuit 204 whichis provided following a rectifier circuit 27 (203), which makes itpossible to miniaturize the elements in the pressure protection circuit30. Owing to it, a wireless chip 202 can be constituted small and in theresult, it is made possible to cut down the cost of the IC card, notonly that of the chip.

FIG. 8(a) shows a concrete form of the variable impedance circuit 30shown in FIG. 4 in the second embodiment 2. The variable impedancecircuit 30 is constituted with the circuit elements as described below:2 circuit elements, a capacitor C1 and an electron switch S1 beingconnected in series, and a capacitor C2 and an electron switch S2 beingconnected in series, are connected to the coil 26 in parallel. Theseelectron switches, S1 and S2, are ON-OFF controlled by a control signalfrom the control circuit 32. In the constitution as mentioned in theabove, in the same way as the first embodiment shown in FIG. 5, it ispossible to control the rectified induced voltage VL obtained from therectifier circuit 27 to be in the allowable voltage range, from Vmin toVmax, even when the coil 26 on the IC card 2 is made to be in a closeproximity to the coil 24 of the power supply circuit 21, which will beunderstood from the relation shown in FIG. 7(b). In the case of thesecond embodiment, in comparison with the case of the first embodiment,the temperature rise can be controlled to be low, which means theupgrade in reliability. In order to realize the second embodiment,however, it is indispensable to have a technology of manufacturing avariable capacitor of a miniature size.

FIG. 9 shows a concrete form of the variable impedance circuit 30 shownin FIG. 4 in a third embodiment. The variable impedance circuit 30 isconstituted as shown in the following: terminals, T1, T2 and T3 areformed corresponding the length of the coil 26 and an electron switch Stwhich is able to change over the connection to T1, T2 or T3 is provided,the switch St which can be changed over by a control signal from thecontrol circuit 32. In the constitution as mentioned in the above, it isalso possible to vary the high frequency power induced in the coil 26;therefore, it is also made possible to control the rectified inducedvoltage VL obtained from the rectifier circuit 27 to be in the allowablevoltage range even when the coil 26 on the IC card 2 made to be in aclose proximity to the coil 24 of the power supply circuit 21.

In the next step, a third embodiment of the power transmission controlsystem by radio according to the present invention will be explainedreferring to FIG. 10.

FIG. 10 shows a schematic view of a power transmission control system byradio in a third embodiment according to the present invention. Thepower supply circuit 21 provided in the reader and/or writer 1comprises: a control power supply 22 a which generates a high frequencyvoltage of 13.56 MHz of a variable voltage, a matching circuit 23 forimpedance matching, a coil 24 for transmitting a radio wave of 13.56 MHzin a power level of approximately 2 to 5 W, a receiving coil(coil-shaped, or spiral-shaped antenna) 37 and a receiving circuit 38for receiving a radio signal concerning an induced voltage transmittedfrom the IC card 2, and a control circuit 39 which controls the highfrequency voltage output from the control power supply 22 a based on theinduced voltage value received in the receiving circuit 38. The inducedvoltage generator portion 28 b on the IC card 2 is composed of a coil26, a rectifier circuit 27 shown in FIG. 2 and the circuits as shown inthe following: a voltage detector circuit 31 which detects a rectifiedinduced voltage VL obtained from the rectifier circuit 27, atransmitting circuit 35 for transmitting a signal concerning the valueof an induced voltage detected in the voltage detector circuit 31 to thecoil 37 of the power supply circuit 21 a by a radio wave, and a coil(coil-shaped or spiral-shaped antenna) 36. The internal circuit 29 onthe IC card 2 is the same as that shown in FIG. 2.

In the constitution as mentioned in the above, the voltage detectorcircuit 31 detects a rectified induced voltage VL obtained from therectifier circuit 27, a signal concerning the detected induced voltagevalue is transmitted to the coil 37 of the power supply circuit 21 a bythe transmitting circuit 35 and the coil 36 by radio to be received bythe coil 37 and receiving circuit 38.

The control circuit 39 detects the deviation of the rectified inducedvoltage VL out of the allowable range of the rectified induced voltagevalue, from Vmin to Vmax, base on the signal of the rectified inducedvoltage value received in the receiving circuit 38 and controls the highfrequency voltage of the control power supply 22 a, and the controlledhigh frequency power transmitted from the coil 24 to the coil 26 issupplied to the rectifier circuit 27; therefore, a voltage with a valuein the range of allowable induced voltage value can be constantlyobtained from the rectifier circuit 27. In the result, even when thedistance between the reader and/or writer 1 and the IC card 2 approachesto the order of 5 cm, it is possible to supply a voltage in theallowable range to the internal circuit 29.

In the next step, a fourth embodiment of the power transmission controlsystem by radio according to the present invention will be explainedreferring to FIG. 11. FIG. 11 shows a schematic view of a fifthembodiment of the power transmission control system by radio accordingto the present invention. The power supply circuit 21 b provided in thereader and/or writer 1 comprises: a control power supply 22 a whichgenerates a high frequency variable voltage of 13.56 MHz, a matchingcircuit 23 for impedance matching, a coil 24 for transmitting highfrequency power having the frequency of 13.56 MHz and power level ofabout 2 to 5 W. a sensor circuit 41 which detects an instantaneousdistance from a passing IC card 2 using infrared rays or ultrasonicwaves, a position detector circuit 42 which calculates an instantaneousdistance (position) from a passing IC card 2 using a signal obtainedfrom the sensor circuit 41, and a control circuit 39 which controls thehigh frequency voltage of the control power supply 22 a based on theinformation of an instantaneous distance d (position) from an passing ICcard 2 detected in the position detector circuit 42. The induced voltagegenerator portion 28 on the IC card 2 is composed of the coil 26 and therectifier circuit 27 shown in FIG. 2.

In the constitution as mentioned in the above, it is possible toconstantly obtain a voltage which is in the allowable range of therectified induced voltage value from the rectifier circuit 27 by anarrangement as shown in the following: the sensor circuit 41 detects theinstantaneous distance from a passing IC card 2 using infrared rays orultrasonic waves, with the detected signal, the position detectorcircuit 42 calculates an instantaneous distance (position) from thepassing IC card 2, the control circuit 39 calculates a high frequencyvoltage value to be generated from the control power supply 22 a fromthe relation between the distance d and the rectified induced voltage VLshown in FIG. 3 based on the information of an instantaneous distance(position) d from the IC card 2 calculated in the position detectorcircuit 42, and controls to generate the calculated high frequencyvoltage value from the control power supply 22 a, and also controls thehigh frequency power to be transmitted from the coil 24 to the coil 26to supply the controlled power to the rectifier circuit 27. In theresult, even when the distance between the reader and/or writer 1 andthe IC card 2 approaches to about 5 cm, it is made possible to supply avoltage in the allowable range to the internal circuit 29.

In the next step, the whole of the system according to the presentinvention including the part in which the information concerning railwaytickets or commutation tickets is communicated by radio and an IC cardperforms the role of a railway ticket or commutation ticket will beexplained in the following. FIG. 12 shows a schematic view of a firstembodiment concerning the whole system including the part in which theinformation concerning railway tickets or commutation tickets iscommunicated by radio and an IC card performs the role of a railwaytickets or commutation ticket.

The reader and/or writer 1 comprises, besides the power supply circuit21, an information transmitter-receiver portion 51 which communicateswith the IC card 2 about the information by radio. The informationtransmitter-receiver portion 51 is connected to a communication networkand a mechanism to open or close a wicket door or a display device, andoutputs data to be transmitted to the IC card 2 to a modulator portion54 and is composed of the following: a CPU 52 which processes dataobtained from a demodulator portion 55 and outputs them, a memory 53which stores data or processing program data obtained from the IC card2, a modulator portion 54 which modulates the data from the CPU 52 with3.39 MHz to transmit the data to the IC card 2, an amplifier 56 whichamplifies the modulated data in the modulator portion 54, a coil 59which exchanges data by radio with the IC card 2, an amplifier 57 whichamplifies the data received by the coil 59, a demodulator portion 55 todemodulate the signal amplified in the amplifier 57 with 3.39 MHz, and amatching circuit 58 for impedance matching.

The IC card 2 comprises an induced voltage generator portion 28 and aninternal circuit 29, and the internal circuit 29 is composed of thefollowing: a memory 63 which stores data concerning railway tickets,commutation tickets, etc., a CPU 62 which controls the memory 63concerning read, write, etc., a modulator portion 65 which modulates thedata read from the memory 63 with a signal of 3.39 MHz, an amplifier 67which amplifies the signal from the modulator portion 65, a coil 69which exchanges data by radio with the coil 59 of the data receiving andtransmitting portion 51, an amplifier 66 which amplifies the datareceived by the coil 69, a demodulator portion 64 which demodulates thesignal amplified in the amplifier 66 with 3.39 MHz, and a matchingcircuit 68 for impedance matching.

In the constitution as mentioned in the above, power is transmitted byradio from the reader and/or writer 1 provided at a gate in a railwaystation or on a bus to an IC card which is passed the reader and/orwriter with noncontact or in the proximity to it, a stabilized DCvoltage of 7 to 15 volt is supplied to the internal circuit on the ICcard 2, which makes it possible to let the internal circuit 29 includingthe CPU 62, etc. operate stably. In the result, it is made possible thatan IC card 2 is able to exchange data by radio concerning railwaytickets, commutation tickets, etc. with the reader and/or writerprovided at a wicket or on a bus when the IC card 2, being held by auser, is passed the reader and/or writer with noncontact or at adistance of about 5 to 20 cm; thereby, it is made possible that an ICcard 2 functions as a railway ticket or a commutation ticket.

FIG. 13 shows the state of one or two circuit chips 70 mounted withparts such as the coil 26, the coil 69, and other circuits, 28, 27, 29,and 32, being connected to the coil 26 and the coil 69.

In the case of the embodiment shown in FIG. 9, the length of the coil 26will be lengthened by increasing number of turns and taps, T1, T2 and T3will be provided to input to the circuit chip 70.

FIG. 14 shows a schematic view of an embodiment concerning the wholeincluding a part where an IC card functions the role of a railwayticket, commutation ticket, or the like in exchanging data concerningrailway tickets, commutation tickets, etc. with a reader and/or writerby radio. The second embodiment shown in FIG. 14 shows the case whereboth transmission of power and communication are performed using a radiowave being composed of a power transmission wave and data communicationmodulated wave as shown in FIG. 15 between a R/W coil (coil-shaped orspiral-shaped R/W antenna) 101 provided on the R/W unit 1 and a cardcoil (coil-shaped or spiral-shaped card antenna) 201 provided on an ICcard 2. As shown in the above, in the ASK modulation system, the powertransmission wave and the signal wave have different frequencycomponents seen from a frequency region, but seen from a time regiononly the amplitude of the power transmission wave varies correspondingto the signal speed. In other words, in the time region, the modulatedwave of the power transmission wave multiplied by the signal wave isseen as if only the amplitude is varied up and down. When the modulatedwave is transmitted by radio, it can be considered to use separateantennas respectively, but in the present invention, in order tosimplify the noncontact card 2 (proximity radio card, IC card), thefield intensity is limited to be within the range decided by theWireless Telegraphy Act (500 μV at a distance of 3m) and a singleantenna (R/W coil) is used to transmit the modulated wave.

The R/W (reader and/or writer) unit 1 comprises the following: a powersupply 105 which generates a high frequency voltage of 13.56 MHz, anencoder circuit 107 which encodes input data 106 to be transmitted to aproximity radio card 2, a modulator 108 which superimposes a voltagebeing amplitude modulated (amplitude shift keying modulation) by asignal encoded in the encoder circuit 107 upon a high frequency voltageof 13.56 MHz generated in the power supply 105, a transmitting amplifier109 which amplifies a signal ASK-modulated and superimposed upon thehigh frequency voltage of 13.56 MHz in the modulator 108, an impedancematching circuit (feeding circuit) 102 having a capacitor 104 and beingcoupled with a signal amplified in the transmitting amplifier 109through an inductance coupling 103, a R/W coil 101 which generates aradio wave to transmit power and data corresponding to the output of thematching circuit 102 and receives data transmitted from the card coil201 of the proximity radio card 2 by a radio wave, a filter circuit 110which removes noise from a signal received by the R/W coil 101 andtransferred through the inductance coupling 103 passing through thematching circuit 102, a receiving amplifier 111 which amplifies a signalobtained from the filter circuit 110, a demodulator 112 whichdemodulates a signal amplified by the receiving amplifier 111 using asignal of high frequency voltage of 13.56 MHz obtained from the powersupply 105, and a decoder circuit 113 which outputs a signal as receiveddata 112 in decoding a signal demodulated in the demodulator 112.

A proximity radio card (noncontact card, IC card) 2 comprises a cardcoil 201, radio chip 202 and a CPU+interface chip 210. The radio chip202 and the CPU+interface chip 210 can be constituted with one chip byminiaturizing the radio chip 202.

The card coil 201 receives a radio wave generated to performtransmission of power and data from the R/W coil 101 in the R/W unit 1,and generates a radio wave corresponding to the transmitting data whichis processed by load-switching modulation.

The radio chip 202 comprises: an impedance matching and rectifiercircuit 203 which functions as a rectifier for the power signal of 13.56MHz received by the card coil 201 and also functions as a matchingcircuit for the transmitting and receiving signal, a constant voltagepower supply circuit 204 which supplies a constant DC voltage 205 ofabout 2 to 5 V at a power level of about 5 mW obtained from a rectifiedinduced voltage output from the matching and rectifier circuit 203, avoltage detector circuit 31 which detects the comparison data betweenthe DC voltage VL obtained from the matching and rectifier circuit 203and a standard (reference) voltager a variable impedance control circuit30 being composed of variable resistor elements such as FET whichsupplies DC power to the IC chips, 202 and 210, as a DC power supplyvoltage 205 in controlling the DC voltage output from the constantvoltage power supply circuit 204 in varying its impedance based on theDC voltage detected in the voltage detector circuit 31, a clock signalextracting circuit 206 which extracts a clock signal from a receivingsignal obtained from the card coil 201, an LPF circuit 207 which removesnoise component from the receiving signal obtained from the card coil201, a waveform shaping circuit 208 which shapes the waveform of areceiving signal obtained from the LPF circuit 207, a load switchingmodulator circuit 209 which modulates a transmitting signal and suppliesthe modulated signal to the card coil 201 through the matching andrectifier circuit 203.

The CPU+interface chip 210 is composed of a frequency divider circuit211 which generates a signal for operating the microcomputer 214 individing the frequency of a clock signal extracted by the clock signalextracting circuit 206 of the radio chip 202, a decoder circuit 212which decodes a signal obtained from the waveform shaping circuit 208 ofthe radio chip 202, a receiving data control circuit 213 which controlsdecoded data (receiving data) obtained from the decoder circuit 212 andinputs the data to the microcomputer 214, a transmitting data controlcircuit 215 which obtains data from the microcomputer 214 in controllingthe transmitting data, an encoder circuit 216 which encodes transmittingdata obtained from the transmitting data control circuit 215 incontrolling them and inputs the data to the load switching modulatorcircuit 209 of the radio chip 202, and a microcomputer 214 of H8, etc.which comprises a built-in memory for storing information as a card andperforms the processing of transmitting and receiving data and thetransfer of data with the memory; thereby the CPU+interface chip 210will be supplied with a stable power supply voltage 205 from theconstant voltage power supply circuit 204 on the radio chip 202.

The purpose of using the R/W coil 101 and the card coil 201 fortransmitting power by a radio wave is to upgrade the efficiency of powertransmission in a short range. When the coil 201 is formed on theproximity radio card, it helps the card to be strong againstdeformation. Both R/W coil 101 and card coil 201 can be formed withspiral antennas.

Even in a case where the distance between the IC card 2 and the readerand/or writer 1 is extremely large, in order to be able to supply adesired DC voltage to the internal circuits, 210 and 202 (29), aresonance circuit is formed in the card coil 201 in connecting a tuningcapacitor to it. When the card coil 201 is formed to have a multilayeredstructure of more than 2 layers, which can be formed by winding aspiral-shaped antenna coil consecutively in the same direction, theinductance of the coil and the stray capacity among the windings mayconstitute a resonance circuit. As a result, a tuning capacitor 25 maynot be needed or an extremely small one will do the work.

Since a full wave rectifier circuit is employed as the rectifier circuit203, ripples are little and a smoothing capacitor becomes small, so thata smoothing capacitor can be incorporated in a chip in miniaturizing it,which makes it possible to miniaturize the radio chip 202.

In particular, the elements in the pressure protection circuit can beminiaturized by providing a variable impedance circuit 30 composed ofvariable resistor elements after the constant voltage power supplycircuit provided following the rectifier circuit 203, in the result, theradio chip 202 can be formed small and the cost of not only the chip butalso that of the IC card can be decreased, moreover the temperature risein the variable impedance circuit 30 composed of variable resistorelements can be decreased, which will upgrade the reliability of thechip 220.

As explained in the above, in a proximity radio card system, power canbe transmitted by radio, and further information communication by radiocan be performed between the reader and/or writer 1 and the noncontactcard 2 when the noncontact card (proximity radio card , IC card) 2 ismade to approach the reader and/or writer 1. In other words, in aproximity radio card system, a power transmission wave or communicationwave is radiated by a coil or a spiral antenna 101 in a reader and/orwriter, and the radio wave is received by a coil or a spiral antenna 201on the side of a card; thereupon, a voltage is induced which operatesthe circuits on the side of the card and signals are detected.

As explained in the above, according to the present invention, there isan effect that a system can be realized in which power can be stablysupplied by radio from a reader and/or writer device (power transmittingdevice) to the internal circuit on the IC card in miniaturizing theelements in the pressure protection circuit and decreasing thetemperature rise in the variable impedance circuit even when thedistance between the IC card and the reader and/or writer device may belargely varied, In particular, since it is made possible to miniaturizethe elements in the pressure protection circuit and to decrease thetemperature rise in the variable impedance circuit, an IC card can beconstituted with an antenna for receiving a radio wave and the elementsof one chip, which allows to realize a low cost IC card.

According to the present invention, there is an effect that a powertransmission system by radio and an IC card can be realized, wherein theIC card is arranged to be able to perform transmission of power by radiofor the reader and/or writer using a coil-shaped or spiral-shapedantenna coil, and power can be stably supplied by radio from a readerand/or writer device (power transmitting device) to the internal circuiton the IC card by only making the IC card pass the reader and/or writerdevice (power transmitting device) with noncontact or in proximity to itin miniaturizing the elements in the pressure protection circuit,decreasing the temperature rise in the variable impedance circuit, andimproving the responsibility of the system.

According to the present invention, there is an effect that a powertransmission system by radio, an IC card, and an informationcommunication system using the IC card can be realized, wherein eventhough the distance between the IC card and the reader and/or writer maylargely vary, power can be supplied stably to the IC card in decreasingthe temperature rise in the variable impedance circuit by controllingthe induced power received on the IC card side varying the staticcapacity in the circuit According to the present invention, a properpower can be transmitted from the power transmission portion of thereader and/or writer to the IC card by radio by only passing the IC cardthrough the reader and/or writer with noncontact or in proximity to it;thereby, a DC voltage can be stably supplied to the internal circuit ofthe IC card and information communication can be performed with highreliability between the reader and/or writer and the IC card.

According to the present invention, there is an effect that aninformation communication system using an IC card can be realized inwhich information communication can be performed with high reliabilitybetween the reader and/or writer device and the IC card in supplying astabilized power from the reader and/or writer device to the IC cardwith noncontact.

What is claimed is:
 1. A power transmission system in which power istransmitted by radio wave from a power transmission device to an ICcard, said IC card comprising: a converter circuit including a firstantenna having a resonance circuit for receiving said transmitted radiowave and a rectifier circuit which converts an induced power received insaid antenna into a DC voltage in rectifying it, the DC voltage beingsupplied to an internal circuit, a detector circuit portion fordetecting one of the induced power obtained from said first antenna ofthe converter circuit and a voltage corresponding to said induced power,and a transmitting unit which transmits an information by a radio waveto the power transmission device, the information concerning with saidone of the induced power and the voltage detected by said detectorcircuit portion; and said power transmission device comprising: areceiving unit which receives said information by the radio wave beingtransmitted from the transmitting unit of the IC card, a control powersupply circuit which controls an output of high frequency power based onthe information received by receiving unit, and a power transmittingunit having a second antenna for transmitting the output of highfrequency power by the radio wave, the output of high frequency powerbeing controlled by said control power supply circuit.
 2. A powertransmission system in which power is transmitted by radio wave from apower transmission device to an IC card, said IC card comprising; aconverter circuit including a first antenna having a resonance circuitfor receiving said transmitted radio wave and a rectifier circuit whichconverts induced power received in said antenna into a DC voltage inrectifying it, an internal circuit to be supplied with the DC voltagewhich is converted in said rectifier circuit of said convertor circuit,a detector circuit which detects one of said induced power and a voltagecorresponding to said induced power, and a transmission unit whichtransmits an information by a radio wave to said power transmissiondevice, the information concerning with said one of the induced powerand the voltage detected by the detector circuit; and said powertransmission device comprising: a receiving unit which receives saidinformation by the radio wave being transmitted from the transmissionunit of the IC card, a control power supply circuit which controls anoutput of high frequency power based on the information received by thereceiving unit, and a power transmitting unit having a second antennafor transmitting the output of high frequency power by the radio wave,the output of high frequency power being controlled by said controlpower supply circuit.
 3. A power transmission system in which power istransmitted by radio wave having a predetermined high frequency from apower transmission device to an IC card, said IC card comprising: anantenna having a resonance circuit which comprises by connecting inparallel with a coil and a capacitor for receiving said transmittedradio wave and generating an induced voltage; a rectifier circuitportion which converts an induced voltage generated from said antennainto a DC voltage in rectifying it; a detector circuit portion whichdetects an information corresponding to relative distance between the ICcard and the power transmission device; a variable resonance frequencycontrol circuit which controls the induced voltage generated from saidantenna in accordance with shifting resonance frequency of saidresonance circuit by varying one of capacitance of the capacitor andinductance of the coil based on said information corresponding torelative distance detected by the detector circuit portion to controlthe DC voltage obtained from said rectifier circuit; and an internalcircuit to be supplied with a controlled DC voltage being obtained fromsaid rectifier circuit portion.
 4. A power transmission systemcomprising: an IC card comprising: a converter circuit including a firstantenna having a resonance circuit for receiving radio wave beingtransmitted from a power transmission device and a rectifier circuitwhich converts an induced power received in said antenna into a DCvoltage in rectifying it, and an internal circuit to be supplied withthe DC voltage which is converted in said rectifier circuit of saidconverter circuit; and said power transmission device comprising: adetector unit which detects an information corresponding to relativedistance between the IC card and the power transmission device, acontrol power supply circuit which controls by varying a level of a highfrequency power based on the information corresponding to relativedistance detected by the detector unit and generates a controlled levelof the high frequency power, and a power transmitting unit having asecond antenna for transmitting the controlled level of the highfrequency power being generated from said control power supply circuitto the first antenna of the converter circuit of the IC card by theradio wave.
 5. A power transmission system as claimed in claim 4,wherein the detector unit is formed by a distance detector unit whichdetects a relative distance information between the IC card and thepower transmission device.
 6. A power transmission system as claimed inclaim 4, wherein the detector unit is formed by a distance detector unitwhich detects a relative distance information between the IC card andthe power transmission device by using one of infrared rays andultrasonic rays.
 7. A power transmission system as claimed in claim 4,wherein the power transmission device is formed by a reader and/orwriter.